I am not sure if I should post this here but I am so happy that I will and if it’s unappropriate please and administrator can delete it and tell me off!

I have had a problem also with other plugins for forum with the registration emails not being received by my users and could not find a solution. Then, thanks to some post I read yesterday here, I was able to understand the problem (thank you – thank you – thank you!) and finally this is the solution I implemented, for whom may want to try: I installed the plugin: Postman STMP Mailer of WordPress and followed the guidelines to create a google Client ID, then I used the guided configuration. So simple and it worked wonders.!
Hope this can be helpful to all 😉